Certain embodiments of the present invention are directed to cured compositions in which the concentration of particles within the surface region of the cured composition is greater than the concentration in the bulk region of the cured composition. In some embodiments, the cured compositions are formed from components comprising at least one polysiloxane having at least one reactive functional group and a plurality of particles. Embodiments of the present invention also are directed to cured compositions formed from components comprising at least one polysiloxane having at least one reactive functional group, at least one reactant comprising at least one functional group that is reactive with the at least one functional group of the at least one polysiloxane, and a plurality of particles. Other embodiments of the present invention are directed to substrates coated with the aforementioned cured compositions. Further embodiments of the present invention are directed to methods for improving scratch resistance of a substrate. It will be apparent to one of ordinary skill in the art that specific embodiments of the present invention may be directed to some or all of these aspects of the present invention as well as other desirable aspects.
Color-plus-clearcoating systems involving-the application of a colored or pigmented basecoat to a substrate followed by application of a transparent or clearcoat over at least a portion of the basecoat have become increasingly popular as original finishes for a number of consumer products including, for example automotive vehicles. The color-plus-clearcoating systems have outstanding appearance properties such as gloss and distinctness of image, due in large part to the clearcoat. Such color-plus-clearcoating systems have become popular for use with automotive vehicles, aerospace applications, floor coverings such as ceramic tiles and wood flooring, packaging coatings and the like.
Topcoat film-forming compositions, particularly those used to form the transparent clearcoat in color-plus-clearcoating systems for automotive applications, are subject to defects that occur during the assembly process as well as damage from numerous environmental elements. Such defects during the assembly process include paint defects in the application or curing of the basecoat or the clearcoat. Damaging environmental elements include acidic precipitation, exposure to ultraviolet radiation from sunlight, high relative humidity and high temperatures, defects due to contact with objects causing scratching of the coated surface, and defects due to impact with small, hard objects resulting in chipping of the coating surface.
Typically, a harder more highly crosslinked film may exhibit improved scratch resistance, but it is less flexible and much more susceptible to chipping and/or thermal cracking due to embrittlement of the film resulting from a high crosslink density. A softer, less crosslinked film, while not prone to chipping or thermal cracking, is susceptible to scratching, waterspotting, and acid etch due to a low crosslink density of the cured film.
Further, elastomeric automotive parts and accessories, for example elastomeric bumpers and hoods, are typically coated xe2x80x9coff sitexe2x80x9d and shipped to automobile assembly plants. The coating compositions applied to such elastomeric substrates are typically formulated to be very flexible so the coating can bend or flex with the substrate without cracking. To achieve the requisite flexibility, coating compositions for use on elastomeric substrates often are formulated to produce coatings with lower crosslink densities or to include flexibilizing adjuvants which act to lower the overall film glass transition temperature (Tg). While acceptable flexibility properties can be achieved with these formulating techniques, they also can result in softer films that are susceptible to scratching. Consequently, great expense and care must be taken to package the coated parts to prevent scratching of the coated surfaces during shipping to automobile assembly plants.
A number of patents teach the use of a coating comprising a dispersion of colloidal silica in an alcohol-water solution of a partial condensate of a silanol of the formula RSi(OH)3 wherein at least 70 weight percent of the partial condensate is the partial condensate of CH3Si(OH)3. Representative, nonlimiting examples are U.S. Pat. Nos. 3,986,997, 4,027,073, 4,239,738, 4,310,600 and 4,410,594.
U.S. Pat. No. 4,822,828 teaches the use of a vinyl functional silane in an aqueous, radiation curable, coating composition which comprises: (a) from 50 to 85 percent, based on the total weight of the dispersion, of a vinyl functional silane, (b) from 15 to 50 percent, based on the total weight of the dispersion of a multifunctional acrylate, and (c) optionally, from 1 to 3 weight percent of a photoinitiator. The vinyl-functional silane is the partial condensate of silica and a silane, such that at least sixty percent of the silane is a vinyl-functional silane conforming to the formula (R)aSi(Rxe2x80x2)b(Rxe2x80x3)c wherein R is allyl or vinyl functional alkyl; Rxe2x80x2 is hydrolyzable alkoxy or methoxy; Rxe2x80x3 is non-hydrolyzable, saturated alkyl, phenyl, or siloxy, such that a+b+c=4; and axe2x89xa71; bxe2x89xa71; cxe2x89xa70. The patent discloses that these coating compositions may be applied to plastic materials and cured by exposure to ultraviolet or electron beam irradiation to form a substantially clear, abrasion resistant layer.
U.S. Pat. No. 5,154,759 teaches a polish formulation comprising a reactive amine functional silicone polymer and at least one other ingredient normally used in polish formulations. One such ingredient disclosed in the patent is an abrasive, which is taught to be aluminum silicate, diatomaceous earth, pumice, fuller""s earth, bentonite, silica, tripoli, hydrated calcium silicate, chalk, colloidal clay, magnesium oxide red iron oxide, or tin oxide.
U.S. Pat. No. 5,686,012 describes modified particles comprising inorganic colored and/or magnetic particles as core particles, and at least one polysiloxane modified with at least one organic group which is coated on the surfaces of the core particles. The patent also discloses a water-based paint comprising a paint base material and the modified particles as the pigment as well as a process for producing the modified particles.
U.S. Pat. No. 5,853,809 discloses clearcoats in color-plus-clear systems which have improved scratch resistance due to the inclusion in the coating composition of inorganic particles such as colloidal silicas which have been surface modified with a reactive coupling agent via covalent bonding.
Despite recent improvements in color-plus-clearcoating systems, there remains a need in the automotive coatings art for topcoats having good initial scratch resistance as well as enhanced retained scratch resistance without embrittlement of the film due to high crosslink density. Moreover, it would be advantageous to provide topcoats for elastomeric substrates utilized in the automotive industry which are both flexible and resistant to scratching.
In one embodiment, the present invention is directed to cured compositions comprising a plurality of particles throughout the cured composition, wherein a concentration of particles present in a surface region of the cured composition is greater than a concentration of particles present in bulk regions of the cured composition.
In another embodiment, the present invention is directed to cured compositions comprising a plurality of particles throughout the cured composition, wherein a concentration of particles within a surface region of the cured composition is greater than a concentration of particles within a bulk region of the cured composition, said cured composition having a 20xc2x0 gloss of greater than 70.
In another embodiment, the present invention is directed to cured compositions comprising a plurality of particles throughout the cured composition, wherein a concentration of particles within a surface region of the cured composition is greater than a concentration of particles within a bulk region of the cured composition, wherein the cured composition has an initial scratch resistance such that after scratch testing greater than 40 percent of an initial 20xc2x0 gloss is retained, and a retained scratch resistance such that after scratch testing greater than 30 percent of said initial 20xc2x0 gloss is retained.
Additionally, a coated substrate is disclosed to be within the scope of the present invention which comprises a substrate and a cured composition coated over at least a portion of the substrate, the cured composition being any of the foregoing cured compositions according to the present invention. The present invention also provides a method of coating a substrate which comprises forming over at least a portion of the substrate a cured composition, the cured composition being any of the foregoing cured compositions according to the present invention. A coated metallic substrate also is provided which comprises a metallic substrate and a cured composition coated over at least a portion of the metallic substrate, the cured composition being any of the foregoing cured compositions according to the present invention. Coated automotive substrates also are disclosed to be within the present invention which comprise an automotive substrate which is coated, at least in part, by any of the foregoing cured compositions according to the present invention. The present invention also provides methods of making coated automotive substrates comprising obtaining an automotive substrate and forming over at least a portion of the automotive substrate any of the foregoing cured compositions according to the present invention.
Also provided are multi-component composite coating compositions which comprise a basecoat deposited from a pigmented coating composition, and any one of the foregoing cured compositions according to the present invention formed as a topcoat over at least a portion of the basecoat. The present invention also provides methods for making multi-component composite coating compositions comprising: (a) applying a pigmented composition to a substrate to form a basecoat; and (b) applying a topcoating composition over at least a portion of the basecoat, and (c) curing the topcoating composition to form any of the foregoing cured compositions according to the present invention.
Methods of improving the scratch resistance of a polymeric substrate or polymeric coating are disclosed which comprise forming on the polymeric substrate or polymeric coating any of the foregoing cured compositions according to the present invention also are provided in another embodiment of the present invention. The present invention also provides methods for retaining the gloss of a polymeric substrate or polymeric coating over time which comprises forming over at least a portion of the polymeric substrate or polymeric coating any of the foregoing cured compositions according to the present invention. Also provided are methods for revitalizing the gloss of a polymeric substrate or polymeric coating comprising forming over at least a portion of the polymeric substrate or polymeric coating any of the foregoing cured compositions according to the present invention.
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term xe2x80x9cabout.xe2x80x9d Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.